thermal: Introduce dummy functions when thermal is not defined

When CONFIG_THERMAL is not enabled, it is better to introduce
equivalent dummy functions in the exported header than to
introduce #ifdeffery in drivers using the function.

This will prevent issues such as that reported in:
http://www.spinics.net/lists/linux-next/msg31573.html

While at it switch over to IS_ENABLED for thermal macros
to allow for thermal framework to be built as framework
and relevant APIs be usable by relevant drivers as a result.

Reported-by: Guenter Roeck <[e-mail]>
Signed-off-by: Nishanth Menon <[e-mail]>
Signed-off-by: Eduardo Valentin <[e-mail]>

include/linux/thermal.h

···
 }
 
 #endif
+
+#if IS_ENABLED(CONFIG_THERMAL)
 struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
 		void *, struct thermal_zone_device_ops *,
 		const struct thermal_zone_params *, int, int);
···
 		struct thermal_cooling_device *, int);
 void thermal_cdev_update(struct thermal_cooling_device *);
 void thermal_notify_framework(struct thermal_zone_device *, int);
+#else
+static inline struct thermal_zone_device *thermal_zone_device_register(
+	const char *type, int trips, int mask, void *devdata,
+	struct thermal_zone_device_ops *ops,
+	const struct thermal_zone_params *tzp,
+	int passive_delay, int polling_delay)
+{ return ERR_PTR(-ENODEV); }
+static inline void thermal_zone_device_unregister(
+	struct thermal_zone_device *tz)
+{ }
+static inline int thermal_zone_bind_cooling_device(
+	struct thermal_zone_device *tz, int trip,
+	struct thermal_cooling_device *cdev,
+	unsigned long upper, unsigned long lower)
+{ return -ENODEV; }
+static inline int thermal_zone_unbind_cooling_device(
+	struct thermal_zone_device *tz, int trip,
+	struct thermal_cooling_device *cdev)
+{ return -ENODEV; }
+static inline void thermal_zone_device_update(struct thermal_zone_device *tz)
+{ }
+static inline struct thermal_cooling_device *
+thermal_cooling_device_register(char *type, void *devdata,
+	const struct thermal_cooling_device_ops *ops)
+{ return ERR_PTR(-ENODEV); }
+static inline struct thermal_cooling_device *
+thermal_of_cooling_device_register(struct device_node *np,
+	char *type, void *devdata, const struct thermal_cooling_device_ops *ops)
+{ return ERR_PTR(-ENODEV); }
+static inline void thermal_cooling_device_unregister(
+	struct thermal_cooling_device *cdev)
+{ }
+static inline struct thermal_zone_device *thermal_zone_get_zone_by_name(
+		const char *name)
+{ return ERR_PTR(-ENODEV); }
+static inline int thermal_zone_get_temp(
+		struct thermal_zone_device *tz, unsigned long *temp)
+{ return -ENODEV; }
+static inline int get_tz_trend(struct thermal_zone_device *tz, int trip)
+{ return -ENODEV; }
+static inline struct thermal_instance *
+get_thermal_instance(struct thermal_zone_device *tz,
+	struct thermal_cooling_device *cdev, int trip)
+{ return ERR_PTR(-ENODEV); }
+static inline void thermal_cdev_update(struct thermal_cooling_device *cdev)
+{ }
+static inline void thermal_notify_framework(struct thermal_zone_device *tz,
+	int trip)
+{ }
+#endif /* CONFIG_THERMAL */
 
-#ifdef CONFIG_NET
+#if defined(CONFIG_NET) && IS_ENABLED(CONFIG_THERMAL)
 extern int thermal_generate_netlink_event(struct thermal_zone_device *tz,
 						enum events event);
 #else